The invention relates to a drilling tool for machine tools comprising a body of a drill, a cutting head arranged on the front side on the body of the drill, and a rearward drill shank, whereby the body of the drill has at least one chip conveyor groove extending from the cutting head over a part of its length, and, if necessary, at least one functional channel extending from the cutting head to the drill shank. The invention relates furthermore to a method for the production of such a drilling tool.
The known drilling tools of this type are usually produced by a chip-removing method, like turning, milling and drilling. The functional channels are produced in the body of the drill with the aid of a deep-hole drill and receive thereby a circular cross section. Mainly in the case of small drill diameters it is often difficult to house functional channels with a sufficiently large cross-sectional surface in the body of the drill. Furthermore the high production expense is felt to be disadvantageous in the known drilling tools.
Based on this the basic purpose of the invention is to develop a drilling tool with novel contours and a method for a particularly simple production of such drilling tools.
The inventive solution is based on the thinking that the body of the drill with its chip conveyor grooves and its functional channels can be chiplessly produced in a particularly simple manner. In order to achieve this, it is suggested according to the invention that a tubular blank, preferably in the cold state, is loaded on its wall simultaneously on several segments distributed over the periphery and moving axially along the blank surface with radially oscillating shaping forming forces, thereby forming at least one chip conveyor groove and at least one functional channel and/or at least one joint inside of the body of the drill. The tubular blank can thereby consist either of a ductile metal, for example of steel, or can be constructed as a raw product out of a sinterable material.
The often desired helical shape of the body of the drill is made possible by the tubular blank being loaded with oscillating shaping forming forces on forming segments moving both axially and also in peripheral directions along the blank surface, thereby producing at least one helically shaped chip conveyor groove and at least one helically shaped functional channel.
The forming of the tubular blank into the finished body of the drill can basically be done in one step. However, the problem arises thereby that at certain points a relatively large forming degree is necessary, which can result in a local tear formation. This is particularly true in the outlet area of the chip conveyor groove. In order to avoid this disadvantage, it is suggested according to an advantageous development of the invention that the blank is formed in steps in several passages. The blank can be tempered or annealed between two passages in order to remove the material stresses, which had built up earlier during the forming.
The blank is, during the forming process moved advantageously axially relative to the stationary forming segments, and is, if necessary, rotated about its axis relative to these segments. It is thereby possible to automatically rotate the blank about its axis during the forming process under the action of an axial feed force and the forming forces acting on it.
The forming forces, which oscillate advantageously with a frequency of 100 to 2000 Hz, are produced according to a preferred embodiment of the invention by a kneading or hammering works with several forming tools of a rotary kneading machine or a rotary hammering machine, which forming tools extend over each one of the forming segments. At least one chip conveyor groove is thereby produced by a shaping forming tool adapted to the contour of the respective chip conveyor groove, whereby the outlet of the chip conveyor groove at the end of a passage path is determined by the inlet contour of the shaping forming tool. The blank, which is moved in a feed direction, can be automatically rotated about its axis by the shaping forming tool, which engages the partially finished, helically shaped chip conveyor groove, which is to be produced. It is basically also possible to rotate the blank by means of a motor about its axis relative to the kneading or hammering works in dependency of its axial feed path. This enables also the creation of a variable helix pitch of the chip conveyor groove and of the functional channel.
According to a further preferred embodiment of the invention chip conveyor grooves are formed on at least two forming segments, which are spaced from one another in a peripheral direction, into the wall of the blank in such a manner that the wall portions in the area of two opposite-lying chip conveyor grooves sealingly abut one another on their inner surface thereby defining a joint. The respective wall portions can be cold-welded to one another in the area of the joint during the forming process when a chemically activated, oxide-free surface exists at the contacted points. The two wall portions, which abut one another in the area of the joint, can also be soldered to one another. Solder or soldering paste must, prior to the forcing process, be moved in between the wall portions which are to be connected, and must during or after the forming process be heated to a fusion or melting temperature.
Besides the soldering wire or the soldering paste, it is also possible to move in addition other foreign media, like separating means, damping means, or an inner coating into the inside space prior to the forming process. Furthermore at least one shaping insert can be placed into the blank, and can be embedded into the functional channels during the forming process. Rod-shaped, wireshaped, tubular or pearl-chainlike inserts of metal, ceramics, plastic and/or polyfluorotetraethylene can be used thereby. Depending on the use, the inserts can remain in the functional channels or can again be removed therefrom.
A cutting head is formed on or fastened to the front end of the body of the drill and a drill shank on or to the rearward end. It is thereby basically possible that the cutting head is formed chiplessly, preferably with the aid of a compression tool or swage to the body of the drill. As an alternative it is possible for the cutting head and/or the drill shank to be welded to the body of the drill by resistance welding and/or by friction welding. A soldered or glued connection is also possible at this point.
A further alternative embodiment of the invention provides that the cutting head and the drill shank are fastened with at least one tie rod to the body of the drill, which tie rod penetrates through the body of the drill preferably in the area of a functional channel. The tie rod can thereby be tensioned or clamped by screwing, wedging or compressing. It is furthermore possible to initially tension or prestress the tie rod by heating and subsequent cooling off. It is fundamentally also possible to use a tie rod having a hollow design. In reverse, the tie rod can have an outer contour supported in a functional channel leaving outer cavities open.
The material of the finished body of the drill is after the forming process advantageously heat-treated, hardened, sintered, and/or has a slidable and wear-resistant surface coating.
The body of the drill is in the drilling tools of the invention designed as a form part produced out of a tubular blank by rotary kneading or rotary hammering, whereby the functional channels have as a characteristic feature a noncircular cross section with at least one sharp-edged corner. The functional channels are advantageously triangular in cross section with one, two or three curved boundary sides, and with two or three sharp-edged corners. At least one of the boundary sides of the functional channels is curved concavely outwardly. It is thereby mainly the boundary side facing the adjacent chip conveyor groove. A third boundary side can be curved convexly.
According to a preferred embodiment of the invention at least two chip conveyor grooves are formed into the body of the drill, which chip conveyor grooves are defined at their flanks by helically curved lands having a partial-cylindrical outer surface defining flutes. In each land there is arranged a preferably triangular functional channel, which is noncircular in cross section. In the functional channels having a triangular cross section there are provided an outwardly convex outer boundary side, which is partially concentric with respect to the partial cylindrical outer surface, and two inner boundary sides, which follow the outer boundary side, are outwardly at least partially concave, and meet in an acute-angled triangular corner pointing toward the axis of the body of the drill. The two inner boundary sides are thereby essentially parallel with respect to the respectively adjacent flank portions of the chip conveyor grooves.
According to a preferred embodiment of the invention the triangular corners of two adjacent functional channels, which corners face one another, are separated from one another by a joint, whereby the joint extends essentially parallel with respect to the base of the groove of two chip conveyor grooves, which are adjacent to one another.
According to a further modification of the invention, the body of the drill has three chip conveyor grooves, which are defined at their flanks by helically curved lands. In addition, an axis-centrally arranged functional channel, which is triangular in cross section, is provided, the triangular corners of which taper pointedly or acutely radially outwardly and end in each one joint.
The mentioned joints can be closed off by a welding or soldering bridge.
At least one of the flanks of the chip conveyor grooves has advantageously a boundary edge, which is sharp-edged toward the adjacent outer surface of the flute.
A further preferred embodiment of the invention provides that the functional channels end in the area of the shank-side outlet of the chip conveyor grooves steplessly in an enlarged center supply channel. At least one of the functional channels can be loaded with a cooling lubricant through a center channel. The enlarged center channel can in the case of the minimum lubricating technique also be used as a depot for a lubricant. At least one of the functional channels can be equipped with at least one wire-shaped, tubular or cablelike insert preferably of metal, ceramic material and/or plastic.
It is fundamentally possible to fill at least one of the functional channels partially or completely with a filler, for example, designed as a damping medium. The lands can furthermore have, in the area of the partial-cylindrical outer surfaces, recesses for receiving wear-resistant support elements or plankings projecting over the partial-cylindrical outer surface. The chip conveyor grooves can also have recesses extending in the longitudinal direction of the grooves, for example, to receive reinforcing or vibration-hindering, wear-resistant support elements.
The cutting head and/or the drill shank can be chiplessly formed, for example, compressed, welded, soldered, glued or screwed to the body of the drill. Using these manufacturing methods, no metal chips are drawn from the body of the drill. The cutting head and the drill shank can furthermore be connected to the body of the drill with at least one tie rod penetrating through the body.